A Furnace is a special block currently only available in the Indev, Infdev, and Alpha versions of Minecraft. It will also be included in Beta. Before the furnace appeared, smelting was accomplished by creating a fire and dropping the ores into it. The furnace, when right-clicked, has its own smelting menu where smelting operations can be done. It consists of one field for the object that will be smelted, one field for the fuel, and one field for the output object. Logs, planks, sticks, coal, and lava buckets (plus chests, workbenches and fences, none of which are very efficient) are all fuels. Each smelting operation takes 10 seconds.
A pickaxe is required to pick up the furnace. Items inside a furnace will be destroyed when the furnace is destroyed.
Smelting will work when the smelting menu is closed, as long as there are still objects to smelt and there is enough fuel. The fire icon diminishes to represent the fuel burn time. When the fire icon diminishes fully, another fuel item is consumed and the heat is refilled. If all objects are smelted, the furnace will stop using additional fuel. If there is no fuel left, the furnace will become inactive. If a smelting process was running, it will be cancelled and must be redone.
Crafting
| Name | I/O | Description |
|---|---|---|
| Furnace | File:CraftingFurnaceIO.png | Used for smelting. |
Smelting
| Input | » | Output |
|---|---|---|
| File:Ironoreitm.png Iron Ore | 
|
Iron File:Invironingot.png |
| File:Goldoreitm.png Gold Ore |
|
Gold File:Invgoldingot.png |
| File:Sanditm.png Sand |
|
Glass File:Glassitm.png |
| File:Cobblestoneitm.png Cobblestone |
|
Stone File:Stoneitm.png |
| File:Porkitm.png Pork |
|
Grilled Pork File:Grilledporkitm.png |
| File:Clayitem.png Clay |
|
Brick File:Brick single.png |
| File:Invfish.png Fish |
|
Grilled Fish File:Invfishcooked.png |
Fuel efficiency
| Fuel | Burning Time | Number of Operations per Fuel | Amount to Light a Furnace All Night | Seconds per Log** |
|---|---|---|---|---|
| File:Invcoal.png Coal | 80s
|
8
|
6.75
|
-
|
| File:Invplanks.png Plank | 15s
|
1.5
|
36
|
60s
|
| File:Invstick.png Stick | 5s
|
0.5
|
108
|
40s
|
| File:Crafting square Wood.png Log | 15s
|
1.5
|
36
|
15s
|
| File:Invworkbench.png Workbench | 15s
|
1.5
|
36
|
15s
|
| File:Invchest.png Chest | 15s
|
1.5
|
36
|
7.5s
|
| File:Invbookshelf.png Bookshelf | 15s
|
1.5
|
36
|
10s
|
| File:Invjukebox.png Jukebox | 15s
|
1.5
|
36
|
7.5s
|
| File:Invfence.png Fence | 15s
|
1.5
|
36
|
40s
|
| File:Invwoodenstairs.png Wooden Stairs | 15s
|
1.5
|
36
|
26.67s
|
| File:Invbucketlava.png Lava Bucket* | 1000s
|
100
|
0.54
|
-
|
*Note that using a Lava Bucket will not only use the lava, but destroy the bucket as well.
**This column is the unit-of-wood-equivalent. Calculation made once the fuel item is converted back to tree logs.
As a building material
Furnaces take more time to destroy than other blocks. However, since they take eight blocks of cobblestone to create, they are an inefficient building material. They are also weaker against TNT than ordinary stone or cobblestone.
Tips and tricks
- 8 coal will smelt an entire stack of 64 blocks. 43 planks are the next best thing - 43 planks are capable of generating 64.5 smelted blocks. If you want to be really efficient and not lose that half-plank to nothing, put in 44 planks, then take the first two smelted blocks out, and put two extra unsmelted blocks in.
- Remember that meat (like other food items) won't stack. This means that 1 coal will fuel between 6 and 7 units of meat, depending on how fast you are with re-loading the furnace. Sticks come in handy, as two sticks should be enough to cook an eighth unit of meat without too much fuel left over.
- The bonus of using planks is that they are a renewable resource. While there is an abundance of coal in many cave systems, the ever expanding distances to find new deposits quickly outweigh the increased burning duration. Trees, however, can be regrown.
- A single bucket of lava will allow for smelting of 100 blocks. The largest stack of blocks is 64. Considering that each smelting operation takes 10 seconds, to maximize the efficiency of a lava bucket, place a lava bucket with 64 blocks of unsmelted material (such as sand, cobblestone, etc), and return between 6 minutes and 10 minutes 40 seconds later to remove 36 smelted blocks and insert 36 more unsmelted blocks.
- If you are out of smooth stone to make a floor or ceiling, place a spare furnace in the spots needed, as the texture on the top of the furnace is the same as smooth stone.
- As of the Halloween update, furnaces will face towards the player when placed.[1]
- Furnaces are very useful for providing light if you have wood but no coal to make torches with.